Implicit regularization beyond one-loop order: gauge field theories

We extend a constrained version of implicit regularization (CIR) beyond one-loop order for gauge field theories. In this framework, the ultraviolet content of the model is displayed in terms of momentum loop integrals order by order in perturbation theory for any Feynman diagram, while the Ward–Slavnov–Taylor identities are controlled by finite surface terms. To illustrate, we apply CIR to massless abelian gauge field theories (scalar and spinorial QED) to two-loop order and calculate the two-loop beta-function of spinorial QED. PACS  11.10.Gh; 11.15.Bt; 11.15.-q     

The Resurgence Properties of the Incomplete Gamma Function II

In this paper, we derive a new representation for the incomplete gamma function, exploiting the reformulation of the method of steepest descents by Howls 1992. Using this representation, we obtain numerically computable bounds for the remainder term of the asymptotic expansion of the incomplete gamma function with large a and fixed positive λ, and an asymptotic expansion for its late coefficients. We also give a rigorous proof of Dingle's formal result regarding the exponentially improved version of the asymptotic series of .     

Microscopic structures of the B7 phase: AFM and electron microscopy studies

A wide variety of morphologies, such as screw‐like filaments, ribbons, etc., have been observed in polarizing microscopy studies of the B₇ phase in a melt or with free surface. In this paper, we present the results of AFM and scanning electron microscopy measurements of structures formed by a columnar‐type B₇ phase. These measurements are aimed at elucidating the three‐dimensional structure of the observed patterns.     

Electrochemical nanogravimetric study of the electropolymerization of 6-aminoindole and the redox transformations of the polymer formed in aqueous media

The electrochemical quartz crystal nanobalance was employed to study the electropolymerization of 6-aminoindole on gold electrodes in acidic media. Potentiostatic or potential cycling electrooxidation of 6-aminoindole below 0.5 V vs. saturated calomel electrode leads to the formation of multilayer polymeric films, while at higher positive potentials, further oxidation takes place resulting in a different material which remains attached to the metal surface but shows decreased or no redox activity. A mechanism of the redox transformations of poly(6-aminoindole) which involves protonation–deprotonation accompanying the electron transfer is suggested. In this potential range, a yellow-green reversible color change occurs. At higher positive potentials blue-purple, indigo-type compounds are formed, and bond-breaking leads to the decrease of the electroactivity.     

Molecular imaging by Mid-IR laser ablation mass spectrometry

Mid-IR laser ablation at atmospheric pressure (AP) produces a mixture of ions, neutrals, clusters, and particles with a size distribution extending into the nanoparticle range. Using external electric fields the ions can be extracted and sampled by a mass spectrometer. In AP infrared (IR) matrix-assisted laser desorption ionization (MALDI) experiments, the plume was shown to contain an appreciable proportion of ionic components that reflected the composition of the ablated target and enabled mass spectrometric analysis. The detected ion intensities rapidly declined with increasing distance of sampling from the ablated surface to ∼4 mm. This was rationalized in terms of ion recombination and the stopping of the plume expansion by the background gas. In laser ablation electrospray ionization (LAESI) experiments, the ablation plume was intercepted by an electrospray. The neutral particles in the plume were ionized by the charged droplets in the spray and enabled the detection of large molecules (up to 66 kDa). Maximum ion production in LAESI was observed at large (∼15 mm) spray axis to ablated surface distance indicating a radically different ion formation mechanism compared to AP IR-MALDI. The feasibility of molecular imaging by both AP IR-MALDI and LAESI was demonstrated on targets with mock patterns. Presented at the 9-th International Conference on Laser Ablation, 2007 Tenerife, Canary Islands, Spain     

Multistage polar switching in bent-core mesogens

We report a novel type of electro-optical switching in a tilted smectic phase of bent-shaped mesogens. The switching consists of a continuous stage and two bistable transitions. Detailed optical and electro-optical measurements using high-speed imaging are given and possible interpretations of the experimental results are discussed.     

Gauge invariance and the CPT and Lorentz violating induced Chern–Simons-like term in extended QED

The radiative induction of the CPT and Lorentz violating Chern–Simons (CS) term is reassessed. The massless and massive models are studied. Special attention is given to the preservation of gauge symmetry at higher orders in the background vector b _μ when radiative corrections are considered. Both the study of the odd and even parity sectors of the complete vacuum polarization tensor at one-loop order and a non-perturbative analysis show that this symmetry must be preserved by quantum corrections. As a complement we obtain the result that transversality of the polarization tensor does not fix the value of the coefficient of the induced CS term.